In conventional key duplicating machines, there are two methods for cutting new keys. The first method is to duplicate a key from a master key in which a guide is used to follow along the surface of the bitted edge of the master key with the movements of the guide being duplicated by a cutting tool cutting into a blank side edge of the key being cut. The master key and the key being cut are both held in key clamps or vice jaw with a shoulder of the key or a tip or nose of the key contacting an abutment and the key being clamped in alignment with the vice jaw. In order to place the key in alignment with the vice jaw, the heel or flat second side of a single-sided key is placed against a key rest both in the case of the master key and in the case of the key to be cut.
In the case of a double-sided key, the groove of the key (also known as the ward), is aligned with an edge of the vice jaw as the key is inserted into the vice jaw with the shoulder or tip positioned against an abutment in a fixed relation to the vice jaw. This is done both for the master key and for the key to be copied. In this way, the fixed relation between the follower guide, which follows the bitted edge of the master key, and the cutting tool results in an exact copy of the same bitted edge. It is also a relatively straightforward task for the operator to align each such key with the same groove edge aligned with respect to an edge of the vice jaw.
In the second method, a key is cut by code, and the exact shape of the key is not cut by following a master key, but rather by following a series of known dimensions describing the shape of the bitted edge which are used to program a predetermined sequence of movements to cut the blank edge of the key for use with a specific lock. When cutting a double-sided key using a coded cutting machine, it is conventionally necessary for the operator to carry out a preliminary position adjustment in order to bring the key as mounted in the vice jaw into a predetermined initial position which, in the case of a single-sided key, would have been determined by placing the key in abutment with the key rest. While such an alignment step is crucial, there exists no easy or automatic way to achieve it.
Standard key codes are referenced with respect to the blank edge opposite the side of the key to be cut, and not with respect to the surface of the blank edge to be cut. This means that the dimension of the bitted edge are not specified by the depths of the cuts to be made, but rather by the amount of key remaining uncut with respect to the opposite side. Such codes are well known in the art and typically comprise a series of precise values for each of the possible "depths" and spaces of the bitted edge of keys of the same series, and then the code for a particular key is merely a set of numbers referring to the particular depth selected for each position or space along the key side edge.
Positioning a key blank in the key cutting machine's vise jaw for a single sided key is a relatively easy task. The key blank is positioned with its side opposite the side to be cut against a keyrest having a known fixed position with respect to the vise jaw, and the key is cut according to the code. In the case of a double sided key, the second side to be cut needs to be placed in the vise jaw as if the first side were uncut and positioned against the keyrest. However, since the first side is already cut, another awkward guide needs to be used to set the key blank in the vise jaw so that it can be cut according to the code.
It is also known in the art to provide key cutting machinery which detects the placement of a key in a vice jaw or which detects a profile of the bitted edge held in the vice jaw. See, for example, U.S. Pat. No. 3,865,011 and U.S. Pat. No. 5,128,531.